Multiple sources

When there are multiple sound sources, the total power emitted is the sum of the power from each source.

By how much would the sound level increase when two sources sound simultaneously with equal power?

• the sound power level would double,
  

  $$L_W =$$

  $$=$$

  $$= ,$$

  
  and there would be an increase of 3 dB.

Similarly, there would be a 3 dB increase in the sound intensity level measured at some distance away from the source.

This accounts for most cases; the actual result depends on correlation (and interference) of sound sources.